1. Field of the Invention
This invention generally relates to a robotic carriage capable of traversing the length of structural members used in the construction industry to collect data and to perform tasks. The invention is specifically concerned with a robotic carriage capable of carrying a surveying target at a known height to selected locations along the length of a large span structural beam so that the camber of the beam can be determined.
2. Description of Related Art
In the construction industry, and bridge building in particular, when large span structural beams are set in place, their camber must be assessed. Camber refers to a deliberately imposed and carefully calculated arching of structural beams in a direction opposite to the load forces that will ultimately be applied to the beams so that the beams deflect to desired position when the load forces are applied. The field measurement of camber is compared to engineering calculations of the desired camber, and the results used in further construction actions to insure proper deck thickness and elevation.
The customary method used after beams are positioned atop their support structures is to recall the surveyors or field engineers to obtain elevation data at specified intervals along the top flange of each beam relative to a datum plan grade line. This is usually accomplished by use of a surveying device, such as Topcon™ model ATF30, in combination with a standard engineering level rod. The location of the elevation readings must be provided atop the beam for use by future workers. This is usually done by workmen walking along the top of the beam using a measuring tape to locate the required intervals and applying a spot of paint or ink at each location. A growing number of field engineers use a laser operated survey instrument, such as Leica™ model TPS 1100, which is capable of locking onto a surveying target such as a prism and automatically following its movement, thereby providing measurement of required intervals as well as the elevation data. Both methods, however, require construction personnel to wear a fall protection safety harness and lanyard that is attached to a secured cable extending the length of the area of interest, and to collect the data by the standard method of first locating the points along the beam where elevations are required with measuring tape and paint. The data is then collected by one person observing the rod readings through the Auto-Level from a remote location while another person walks atop the beam carrying the rod to the pre-marked locations to be observed. If a laser operated surveying station is used, the marking of the locations need not be a separate operation, since the worker carrying the prism and its pole with recording device would then have a marking device to carry and apply also.
These prior art methods are not only labor intensive and costly in both time and man-power but also present a serious risk to the safety of the worker when walking over a narrow top surface high above the ground. Worse yet, the top of such beams often includes vertical shear studs that pose a tripping hazard to workmen. Since such beams often span over automobile or pedestrian traffic, there is a further safety risk posed by the accidental dropping of level rods or prism poles from the substantial heights of such beams.
Accordingly, there is a need for a robotic device which can move a level rod, reflective prism, video camera, or other data collection device across the length of a large span beam without jeopardizing the safety of construction workers or traffic passing beneath the beam. Ideally, such a device should be able to reliably traverse the length of a variety of types of beams having different patterns of vertically extending shear studs, as well as beams having no shear studs at all. It would further be desirable if the device were compatible with commercially available surveying equipment.